Offshore drilling system



June 29, 1965- R. o. POLLARD ETAL 3,191,696

OFFSHORE DRILLING SYSTEM Filed May 16, 1958 5 Sheets-Sheet 2 25 2a 25 a 1 v I j 24- 'FQ'G. 7. 2/

INVENTORS wa er-a. #044,020

June 29, 1965 R. o. POLLARD ETAL 3,191,696

OFFSHORE DRILLING SYSTEM Filed May 16, 1958 5 Sheets-Sheet 3 l N VEN TORS @055e70. POLL/42D g/4 2455 e. 64L,./Q.

14 7 mQ/VE VS June 29, 1965 R. o. POLLARD ETAL 3,191,696

OFFSHORE DRILLING SYSTEM 5 Sheets-Sheet 4 Filed May 16, 1958 0 5 m WZ N m 0 7 r5 Mp 8 5 Z 6 4 k B w o w x wa a a y 3 1---: 6 W W. i; 6 6 6 5 June 1965 R. O. POLLARD ETAL 3,191,696

OFFSHORE DRILLING SYSTEM Filed May .16, 1958 Sheets-Sheet 5 U I u I I 62 65 l :62: I 9 65 a i I F76. 6. v i v 56 .5/ 4 INVENTORS we e. azzflep 55 W55 2. 5444, .72.

prrozn/ys United States Patent 3,191,696 OFFSHORE DRHJLING SYSTEM Robert 0. Pollard, Downey, and Charles R. Ball, J12, Oiai,

Calif., assignors to Richfield Oil Corporation, Los Allgeles, Califi, a corporation of Delaware Filed May 16, 1958, Ser. No. 735,346 8 Claims. (Cl. 175-7) This invention relates to the drilling of underwater wells from floating vessels, and is particularly directed to improvements in methods and apparatus for guiding the lower end of a drill string into a well hole in a formation underlying a body of water.

The drilling of wells in offshore marine locations from equipment located on floating vessels requires some form of guide to align the lower end of the drill string with the hole in the ocean floor each time that the bit is changed and the drill pipe is to be relowered into the hole. The patents to McNeill, Re. 24,083 and Bauer et al. No. 2,808,229 show guide devices for this purpose, but which depend on sliding contact between the guiding and guided parts. Experience has shown that these early proposals are not reliable in service and sometimes result in costly malfunction of inaccessible parts adjacent the ocean floor. Extensive damage to well head equipment may occur if the lower end of the drilling string should bypass the opening. The damage may be very costly to repair or in some instances may be so severe as to require abandonment of the underwater drill site and total loss of well head equipment. It is the principal object of the present invention to provide a dependable method and apparatus for guiding the lower end of the drilling string into the central opening in the well head equipment on the ocean floor. Related objects and advantages will appear hereinafter.

The drawings illustrate a preferred form of apparatus for carrying out the method.

FIGURE 1 is a side elevation partly in section showing diagrammatically the guide apparatus of the present invention with the landing base about to be lowered into position on the ocean floor.

FIGURE 2 is a view similar to FIGURE 1 showing the landing base in operative position on the ocean floor.

FIGURE 3 is a view similar to FIG. 2 showing the drill string and the position of the parts during initial drillingof the hole in the ocean floor.

FIGURE 3A is a plan view of a bushing shown in FIGURES 3 and 4.

FIGURE 4 is a side elevation partly in section of drilling apparatus according to the present invention showing diagrammatically, the conductor casing after it has been cemented in. place, and the setting tool in the operation of being raised after disconnection from the conductor casing.

FIGURE 5 is a side elevation partly in section, showing the well head equipment being lowered into position to engage the upper end of the conductor casing.

FIGURE 6 shows in partial sectional elevation the well head equipment in place on the ocean floor and with the drill bit on bottom in the operation of drilling below the conductor casing with all control equipment in position.

FIGURE 7 shows in partial sectional elevation, the bit being withdrawn from the drilling head 57 after a period of use.

Briefly stated, the method and apparatus of this invention contemplates the use of yoke means for guiding the lower end of the drilling string into the well head equipment on the ocean floor. The yoke is pulled down by a pair of flexible cables each of which extends under a sheave or pulley mounted on a landing base positioned on the ocean floor. The cables extend from the sheaves or pulleys upward to the floating vessel and are spooled on power operated constant tension winches. Conventional rotary drilling equipment is carried on the floating vessel. When the bit has been changed and the drill pipe is to be rerun into the hole, the yoke means are placed in position around the bit and the winches are operated to spool up the guide cables, thereby acting to pull the yoke means and drill pipe downward. A conventional hoist on the floating vessel resists the lowering movement of the drill pipe, and the drill pipe is thereby maintained in tension. The yoke means and landing base have interengaging parts which are brought into registry, and the bit at the lower end of the drilling string is thereby accurately centered to pass through the interior of the well head equipment and through the conductor casing into the Well hole.

Proceeding to a more detailed description in connection with the accompanying drawings, the landing base generally designated 10 may comprise a steel framework 11 weighted by a concrete block 12. The lower face of the block 12 is large enough to prevent it from sinking into the floor of the ocean. The landing base is pro vided with a central opening 13 defined within a metallic sleeve 14 forming a part of the framework 11. A metal lic conical member 15 above the block 12 is connected to the upper end of the sleeve 14 after the manner of a funnel. A pair of upright sockets 16 are secured to the flaring end of the conical member 15 in diametrically opposite positions. Sheaves 17 are rotatably mounted on the landing base as shown below the sockets and a pair of flexible cables 18 extend under the sheaves 17 and pass upward through socket parts 16.

The yoke generally designated 20 is provided with laterally spaced depending projections 21 and each of these projections is secured to one of the cables 18. The yoke is provided with a central aperture 22.

A pair of power operated constant tension winches 25 are mounted on the floating vessel generally designated 26. Pulleys 27 also mounted on the vessel 26 assist in.

spooling the cables 18 on the drums of the winches 25.

The winches 25 serve to maintain the tension of the cables 18 at a substantially constant value with the rise and fall of the floating vessel 26 under wave and tide action.

from the yoke by means of the cables 18 and sheaves 17. I

. The winches 25 are then operated to unspool the cables 18, thereby allowing the landing base 11 to be lowered through the water and to come to rest upon the ocean floor 29. p

The rotary drilling string generally designated 30 is made up of conventional drill pipe sections threadedly connected end to end, and one or more drill collars 31.. may be included in the drilling string just above the bit 32. The drill bit' 32 is lowered through the central opening 22 in the yoke 20 and releasable means such asa split or hinged bushing 33 (shown in FIGURE 3A) are then placed in position within the opening 22 and held against displacement by means of the latching parts 34 which may be screwed into yoke 20. The releasable means are associated with the yoke for gripping and pulling the drilling string downwardly. The central opening in the bushing 33 is of smaller size than the maximum lateral dimension of the bit 32 so that the bit 32 will not pass through the bushing 33. After connection of the parts 34, the drilling string 30 including the bit 32, the drill collars 31 and sectional drill pipe are then Patented June 29, 1965.

lowered from the floating vessel by conventional hoisting equipment 37, and the winches acting through cables 18 and yoke 2') apply a downward force to the bit 32 to maintain the drilling string in tension during the lowering movement. The bushing 33 on the yoke 29 remains in contact with the shoulder on the bit 32.

The vertical parts of the cables 18 passing through the sockets 16 and extending from the sheave 17 pull the yoke 20 downward until the projections 21 are received within the sockets 16 on the landing base it This action brings the bit 32 at the lower end of the drilling string 30 into a central position with respect to the opening 13 in the landing base 10. Continued lowering movement of the drilling string 30 brings the bit 32 into engagement with the formation underlying the ocean floor 29. The drilling string 30 is then operated in a conventional manner from equipment on the floating vessel 26 to drill a hole 36 into the ocean floor beneath the landing base 10, as shown in FIGURE 3. Drilling fluid is pumped down the interior of the drilling string 30 in a conventional manner and emerges through holes in the bit 32 and carries cuttings upward through central opening 13 in the landing base 10.

When the hole 36 has reached the desired depth, the drilling string 30 is withdrawn upward by hoisting equipment on the floating vessel 26, and the shoulder 35 on the bit engages under the bushing 33 on the yoke 20. The yoke 20 then travels upward with the lower end of the drilling string as the cables 18 are unspooled from the winches 25, as shown in phantom lines in FIGURE 3. The winches 25 may be air operated, or may be driven from electric motors driving through hydraulic couplings.

Conductor casing 40 is then suspended below the yoke 20 from the vessel 26 and supported by means of a pipe string 41, disconnect coupling 42, and mandrel 40a. The opening in the bushing 33 is smaller than the diameter of the flange 43 at the lower end of the pipe string 41. The conductor casing extends through the central opening 13 on the landing base and the mandrel 49a is provided with a collar 44 which rests on a seat 45 provided on sleeve 14. Cement is then pumped down the interior of the pipe string 41 and emerges through the lower open end of the conductor casing 40 to fill the annular space between the hole 36 and the outer surface of the casing 40. The cement serves to anchor the conductor casing 46 and landing base 10 securely in position on the ocean floor. The disconnect coupling 42 is then actuated, fo example, by turning the pipe string 41 in a direction reverse to the direction the pipe string is turned for drilling. This action separates the pipe string 41 from the conductor casing 40. Pipe string 41 is then raised upward by means of the hoisting equipment on the floating vessel 26. FIGURE 4 shows the position of the parts during this hoisting operation.

It will be observed that mandrel 40a on the upper end of the conductor casing 40 projects above the cylindrical member 14 on the landing base 10, and that this mandrel 40a is provided with a pair of axially spaced enlargements 50 and 51. As shownin FIGURE 5, well head equipment generally designated 52 is lowered into position over the upper'projecting end of the conductor casing mandrel 40a in the manner shown in FIGURE 5. A setting tool 53 consisting of pipe sections connected end to end is used to lower the well head equipment 52 from the floating vessel 26. A collar 54- fixed on the lower portion 55 of the setting tool 53 is received within the bore 56 on the drilling head 57. Releasable pins 58 operated by remote control secure the'collar 54- to the drilling head 57.

The well head equipment 52 includes the drilling head 57, the mud return spacer 59, the bag type blowout preventer 60, the ram type blowout preventers 61 and 62, the spool 62a and the gate valve assembly 63. A pair of parallel tubular guides 64 and 65 are mounted on the assembly 52 and the lower ends of these guides are adapted to be received within the sockets 16 on the landing base 16. The cables 18 are loosely received within the interior of the guides 64 and 65. The assembly 52 also includes the conical member 66 fixed to the upper end of the drilling head 57. A pair of sockets 67 which are similar to the sockets 16 are mounted at the upper end of this conical member 66.

In the operation of lowering the well head equipment 52 into position adjacent the ocean floor 29, the yoke 20 is positioned at the upper end of the assembly 52 with the yoke projections 21 received within the sockets 67. The setting tool 53 is lowered by conventional hoisting equipment on the floating vessel 26 and the winches 25 are operated to tension the cables 18 and setting tool 53. The pins 58 are only a safety device; the blowout preventer 6G is maintained in closed position on the part 55 of the setting tool 53 during the lowering operation. The assembly 52 comes to rest when the shoulder 68 on the enlargement 56 engages the shoulder 69 on the gate valve assembly 63. The ram 70 engages under the shoulder 71 on the conductor casing 49 to anchor the well head equipment 52in operating position and to form a fluid tight seal between the blowout preventer and the casing. The pins 53 and the blowout preventer 60 are then released to permit the setting tool 53 and yoke 26 to be returned to the floating vessel 26. Hydraulic lines are provided for operating the pins, blowout preventers and gate valve, but are omitted from the drawing for clarity.

At this stage in the sequence of operations the control head assembly 52 is in position and'latched to the upper end of the conductor casing 40, and the central opening which extends completely through the assembly 52 is aligned with the central opening in the casing 40. A bushing 33 is then installed in the central opening of the yoke 20to encompass the lower end of the drilling string 30 just above the bit 32. The central opening in the bushing is smaller than the maximum transverse dimension of the bit 32. The yoke 20 is then pulled downward by means of the taut cables 18 and winches 25 while the drilling string is lowered under tension from the floating vessel 26. The projections 21 on the yoke 20 are received within the sockets 67 on the upper end of the well head assembly 52 and downward motion of the yoke 20 ceases at this point. The bit 32 and drilling string 30 are then aligned with the central opening 73 in the assembly 52 and continued downward movement of the drilling string 39 causes the bit 32, drill collars 31 and portions of the sectional drilling string 30 to pass downward through the well head assembly 52.

A rubber sealing assembly 75 is loosely mounted on the drilling string 30 above the drill collars 31 and this rubber seal is received within the bore 56 of the drilling head 57 (see FIGURE 7). The pins 58 automatically engage the groove 76 to maintain the sealing assembly 75 in position. The drilling string 30 rotates within the sealing assembly 75.

When the drilling string 30 is being rotated from the floating vessel 26 and when the bit 32 is on bottom, the drilling fluid which is pumped down through the interior of the drilling string emerges through holes in the bit 32 and passes upward around the drill collars 31 and drill pipe sections and within the conductor casing 40, carrying cuttings trom the bit 32. This drilling fluid passes upward through the blowout preventers 62 and 61 but is prevented from passing out through the upper end of the drilling head 57 by means of the sealing assembly 75. Drilling fluid passes into central opening 73 in the well head equipment 52 and emerges through lateral fitting 77 on the mud return spacer 59. A hose line (not shown) carries the return drilling fluid back to the floating vessel 26. Should the bit 32 encounter a formation containing high pressure gas the blowout preventers 61 and 62 may be operated by remote control in a conventional manner to seal oil the annular space between the drilling string 30 and interior of the blowout preventers.

When the bit 32 has becomedulled after a period of use, the drilling string 30 is raised by conventional hoisting equipment on the floating vessel 26 until the drill collars 31 approach the position of the drilling head 57, The pins 58 are then released by remote control to permit the sealing member 75 to be drawn upward out of the bore 56 as the drilling string 36 is raised. The shoulder at the upper end of the drill collar 31 engages under the sealing assembly 75 and raises it out of the bore 56 and at the same time, the sealing assembly 75 engages under the yoke 20 and raises it upward away from the well head assembly 52. FIGURE 7 shows the parts in this position.

The yoke 20 travels upward with the lower end of the drilling string 30 while the winches 25 maintain substantially constant tension on the cables 18 and while unspooling them from the winch drums. A new bit 32 and a new seal assembly 75 are installed on the drilling string and it is again lowered from the floating vessel 26, using the yoke 20 and pull down cables 1-8 as a means for guiding the bit 32 into the central opening 73 on the well head assembly 52.

While we have described our invention in connection with the drilling of Wells, it will be understood that various features of the method and apparatus may be used for well completion and production practices and that the invention therefore is not limited to drilling operations per se.

Having fully described our invention, it is to be understood that we do not wish to be limited to the details herein set forth, but our invention is of the full scope of the appended claims.

We claim:

1. Apparatus for guiding the lower end of a drilling string from a floating vessel into an opening in submerged well head equipment comprising in combination: a submerged landing base, well head equipment having a central opening therein, a pair of sheaves mounted on the landing base on opposite sides of the central opening, a pair of sockets mounted on the landing base above the sheaves, a yoke releasably suspendable from said vessel having an opening adapted to encompass a portion of the lower end of the drillingstring, releasable means asso ciated with said yoke for gripping and pulling said drill string downwardly, downward extending projections on the yoke, 21 pair of flexible cables secured to one of the projections respectively, the cables each extending through one of the sockets respectively and passing around the sheaves and extending upward to the floating vessel, and winch means on the floating vessel for spooling said cables to lower the yoke and bring the projections into engagement with the sockets.

2. Apparatus for guiding the lower end of a pipe string from a floating vessel into an opening in a submerged member comprising in combination: a submerged stationary member having a central opening therein, a yoke having a central opening and means associated therewith for engaging a portion of the lower end of said pipe string to transmit a downward force thereon, said engaging means permitting said pipe string to pass freely through said yoke downwardly, a pair of flexible cables each secured to said yoke, the cables extending upward from the submerged member to the yoke, cooperating parts on the submerged member and the yoke for laterally centering said yoke relative to said submerged member upon downward movement of said yoke, means for pulling said yoke downward including means at said vessel for tensioning the cables to thereby bring said cooperating parts into engagement when said yoke is pulled downward, and means on the floating vessel for resisting the downward pulling force exerted on said pipe string by said cables.

3. Apparatus for guiding the lower end of a drilling string from a floating vessel into an opening in submerged well head equipment comprising in combination: a submerged landing base, submerged well head equipment having a central opening therein, a yoke having a central opening and means associated therewith for gripping and pulling said drilling string downwardly, said means permitting said drilling string to pass freely through said yoke downwardly, a pair of flexible cables each secured to said yoke, the cables extending upward from the sub merged landing base to the yoke, cooperating parts on the well head equipment and the yoke for laterally centering said yoke relative to said submerged well head equipment upon downward movement of said yoke, means for pulling said yoke downward including means for tensioning the cables to thereby bring said cooperating parts into engagement, and means on the floating vessel for resisting the downward pulling force exerted on said drilling string by said cables.

4. Apparatus for guiding the lower end of a drilling string from a floating vessel into an opening in a submerged member comprising in combination: a submerged landing base having a central opening therein, a pair of sheaves mounted on the landing base on opposite sides of the central opening, a yoke having an opening and means associated therewith for gripping and pulling said drilling string downwardly, said means permitting said drilling string to pass freely through said yoke downwardly, a pair of flexible cables each secured to said yoke and passing around said sheaves and extending upward to the floating vessel for laterally centering said yoke relative to said submerged landing base upon downward movement of said yoke, means for pulling said yoke including winch means on the floating vessel for spooling said cables to lower the yoke and bring the lower end of the drilling string into alignment with the central opening in the landing base.

5. Apparatus for guiding the lower end of a drilling string from a floating vessel into an opening in a submerged member comprising in combination: a submerged landing base having a central opening therein, a pair of sheaves mounted on the landing base on opposite sides of the central opening, a yoke having an opening and means associated therewith for gripping and pulling said drilling string downwardly, said means permitting said drilling string to pass freely through said yoke downwardly, a pair of flexible cables each secured to said yoke and passing around said sheaves and extending upward to the floating vessel, interengageable parts on the yoke and submerged member operable to align the opening in the yoke with the central opening in the landing base upon downward movement of the yoke, means for pulling said yoke downward including winch means on the floating vessel for spooling said cables to lower the yoke and bring the said inter engageable parts into engagement.

6. Apparatus for guiding the lower end of a pipe string from a floating vessel into an opening in a submerged member comprising in combination: a submerged stationary member having a central opening therein, a yoke having a central opening with a bushing therein and means associated therewith for engaging a portion of the lower end of said pipe string to transmit a downwardly force thereon, said engaging means permitting said pipe string to pass freely through said yoke downwardly, flexible cables secured to said yoke, the cables extending upward from the submerged member to the yoke, cooperat ing parts on the submerged member and the yoke for laterally centering said yoke relative to the submerged member upon downward movement of said yoke, means for pulling said yoke downward including means at said vessel for tensioning the cables to thereby bring said cooperating parts into engagement, and means for resisting downward pulling force exerted on said pipe string by said cables.

7. Apparatus for guiding drilling tools from a floating vessel into an opening in a submerged member, comprising in combination: a submerged stationary member having a central opening therein a blowout preventer having a central opening therein registering with the central opening of the stationary member, a yoke positioned above said blowout preventer, means on the yoke to guide said drilling tools downward thereon, a pair of flexible cables each secured to said yoke, said flexible cables extending upward from the submerged member to the yoke, cooperating parts on theblowout preventer and the yoke for aligning said yoke relative to said blowout preventer upon downward movement of said yoke whereby said tools may be guided through said central opening of said blowout preventer and into said submerged member, means for pulling said yoke downward including means at said vessel for tensioning said cables to thereby bring said cooperating parts into engagement when said yoke is pulled downward, and means on .the floating vessel for resisting the downward pulling force exerted on said tools by said cables.

8. A method for guiding a drilling string from a floating vessel into an opening in a submerged member through a blowout preventer with yoke means, comprising the steps of: connecting said blowout preventer to said drill string at the floating vessel, maintaining said yoke means above said blowout preventer while said blowout preventer is lowered to said submerged member, pulling and guiding said drill string and said blowout preventer downward towards the submerged member through the distance between the vessel and the submerged member with cables attached to said yoke means in position above said blowout preventer while partially resisting the downward movestring, and pulling and guiding drill string from said vessel through said blowout preventers with said yoke means.

References Cited by the Examiner UNITED STATES PATENTS 1,766,628 6/30 Grant 175-10 2,798,692 7/57 Thomas 17562 XR 2,808,230 10/57 McNeill et al 175-7 2,984,308 5/61 Bauer et al 175-7 3,012,610 12/61 Bauer et a1 175-7 XR 3,021,909 2/62 Postlewaite 1757 FOREIGN PATENTS 61,371 10/43 Denmark. 160,865 4/61 Great Britain.

CHARLES E. OCONNELL, Primary Examiner.

WALTER BERLOWI i Z, BENJAMIN BENDETT, BEN- JAMIN HERSH, Examiners. 

2. APPARATUS FOR GUIDING THE LOWER END OF A PIPE STRING FROM A FLOATING VESSEL INTO AN OPENING IN A SUBMERGED MEMBER COMPRISING IN COMBINATION: A SUBMERGED STATIONARY MEMBER HAVING A CENTRAL OPENING THEREIN, A YOKE HAVING A CENTRAL OPENING AND MEANS ASSOCIATED THEREWITH FOR ENGAGING A PORTION OF THE LOWER END OF SAID PIPE STRING TO TRANSMIT A DOWNWARD FORCE THEREON, SAID ENGAGING MEANS PERMITTING SAID PIPE STRING TO PASS FREELY THROUGH SAID YOKE DOWNWARDLY, A PAIR OF FLEXIBLE CABLES EACH SECURED TO SAID YOKE, THE CABLES EXTENDING UPWARD FROM THE SUBMERGED MEMBER TO THE YOKE, COOPERATING PARTS ON THE SUBMERGED MEMBER AND THE YOKE FOR LATERALLY CENTERING SAID YOKE RELATIVE TO SAID SUBMERGED MEMBER UPON DOWNWARD MOVEMENT OF SAID YOKE, MEANS FOR PULLING SAID YOKE DOWNWARD INCLUDING MEANS AT SAID VESSEL FOR TENSIONING THE CABLES TO THEREBY BRING SAID COOPERATING PARTS INTO ENGAGEMENT WHEN SAID YOKE IS PULLED DOWNWARD, AND MEANS ON THE FLOATING VESSEL FOR RESISTING THE DOWNWARD PULLING FORCE EXERTED ON SAID PIPE STRING BY SAID CABLES. 